Fuel tank

ABSTRACT

A lower wall ( 8 ) forming a fuel storage chamber ( 5 ) becomes curved downward according to increase of the fuel amount, and at this time a support member ( 23 ) for supporting the fuel storage chamber ( 5 ) does not restrain the downward curvature of the lower wall ( 8 ), whereby the capacity of the fuel storage chamber ( 5 ) can be increased and whereby the amount of the fuel that can be stored in the fuel storage chamber ( 5 ) can be maintained at the maximum, as compared with structure inhibiting deformation of the lower wall ( 8 ).

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a fuel tank for storing fuel.

[0003] 2. Related Background Art

[0004] If there is a space above the fuel level in the fuel tank, thefuel will be evaporated and this evaporated fuel could be emitted to theatmosphere. For example, Japanese Laid-Open Patent Application No.H8-170568 discloses a fuel tank constructed in such structure that afuel storage chamber for storing the fuel is made of an extensibleenvelope film and that the envelope film expands and contracts accordingto the amount of the fuel in the fuel storage chamber, therebypreventing the evaporated fuel from appearing above the fuel level inthe fuel storage chamber. Specifically, the above envelope film iscomposed of an upper wall, a lower wall, and a side wall of a bellowsshape connecting these upper wall and lower wall to each other, and thelower wall of the envelope film is attached to a flat bottom wall of ahousing. The upper wall of the envelope film moves up and down in thehousing, depending upon the fuel amount in the fuel storage chamber, andthe side wall expands and contracts with the up and down motion of theupper wall. The capacity of the fuel storage chamber thus increases anddecreases with the upper and down motion of the upper wall and theexpansion and contraction of the side wall of the envelope film.

SUMMARY OF THE INVENTION

[0005] The inventor, however, found out the fact that, because in theabove fuel tank the lower wall of the envelope film forming the fuelstorage chamber was fixed to the bottom wall of the housing, the lowerwall was not displaced or deformed according to the fuel amount in thefuel storage chamber and the maximum amount of the fuel that was able tobe stored in the fuel storage chamber of the above fuel tank was thussmaller than the maximum that would have been expected if the lower wallshould have been displaceable or deformable in the direction to increasethe capacity of the fuel storage chamber, according to the fuel amountin the fuel storage chamber.

[0006] The present invention has been accomplished in order to solve theabove issue and an object of the invention is to provide a fuel tankprovided with a fuel storage chamber that is deformable according to theamount of fuel stored therein, wherein the amount of the fuel that canbe stored in the fuel storage chamber is maintained at the maximum.

[0007] A fuel tank of the present invention is a fuel tank comprising afuel storage chamber that is deformable according to the amount of fuelstored therein, wherein the fuel storage chamber comprises a lower wallto be curved downward according to increase in the amount of fuel and issupported by a support member that allows the lower wall to be curveddownward.

[0008] Since this fuel tank of the present invention is constructed insuch structure that the lower wall forming the fuel storage chamberbecomes curved downward according to the increase in the amount of fueland that at this time the support member for supporting the fuel storagechamber does not restrain the downward curvature of the lower wall, thecapacity of the fuel storage chamber is increased as compared with thefuel tank not allowing such deformation of the lower wall.

[0009] Specifically, the fuel storage chamber is composed of an upperwall and a lower wall of a polygon opposed to each other, and peripheralwalls connecting these upper wall and lower wall.

[0010] The walls constituting the fuel storage chamber are formed,specifically, in multilayered structure of resin.

[0011] The support member is preferably constructed in structure forsupporting a peripheral part of the fuel storage chamber. When thisstructure is adopted, the support member for supporting the peripheralpart of the fuel storage chamber does not restrain the downwardcurvature of the lower wall and, therefore, the lower wall is wellcurved downward.

[0012] The peripheral part of the fuel storage chamber is composed,specifically, of the peripheral walls, and connecting portions of theupper wall and lower wall connected to the peripheral walls.

[0013] The support member is preferably configured to support corners ofthe peripheral part. When this configuration is employed, the peripheralpart, particularly at the corners, has higher rigidity than the otherportions, because there are the upper wall, the lower wall, and verticalconnecting portions for connecting adjacent peripheral walls. Hence thefuel storage chamber is supported well even by the structure forsupporting only the corners. Since the support member is configured tosupport only the corners of the peripheral part as against the inventionfor supporting the whole of the peripheral part, the configuration ofthe support member is simplified. Even if the peripheral walls aredeformed with deformation of the lower wall, the corners will rarely bedeformed because of their high rigidity as described above. Therefore,the deformation of the peripheral walls and the lower wall is notrestrained even in the structure for supporting the corners.

[0014] In a preferred configuration the peripheral walls have a flangemember and the support member supports the flange member. When thisconfiguration is employed, the support member supporting the flangemember of the peripheral walls does not restrain the downward curvatureof the lower wall and, therefore, the lower wall is well curveddownward.

[0015] The support member is preferably configured to comprise vibrationsuppressing means for suppressing input of vibration from the outside ofthe fuel storage chamber thereinto. When this configuration is adopted,the vibration suppressing means suppresses vibration of the fuel storagechamber and also suppresses production of noise.

[0016] In a preferred configuration the vibration suppressing means isan elastic member and this elastic member supports the fuel storagechamber in a vibration-isolating manner. When this configuration isadopted, the vibration of the fuel storage chamber, for example, due toacceleration G or vertical G is transmitted to the elastic member andelastic action of this elastic member suppresses the vibration of thefuel storage chamber and also suppresses production of noise.

[0017] Here, the elastic member is, specifically, a vibration-isolatingmaterial of rubber.

[0018] Another specific example of the elastic member is a coil spring.

[0019] The support member is preferably an elastically deformablesupport member, which abuts against the lower wall, for supporting thelower wall, the elastically deformable support member being arranged toelastically deform while dispersing a load exerted by the lower wallaccording to the downward curvature of the lower wall. When thisconfiguration is employed, the elastically deformable support member asthe support member abuts against the lower wall and supports the lowerwall with elastically deforming while dispersing the load exerted by thelower wall according to the downward curvature of the lower wall.Therefore, the support member allows the downward curvature of the lowerwall while receiving the weight of the fuel storage chamber includingthe fuel. Thanks to this, the lower wall is well curved downward. Sincethe elastically deformable support member supports the fuel storagechamber while elastically deforming, it suppresses the vibration of thefuel storage chamber and also suppresses the production of noise.

[0020] Here, the elastically deformable support member is, specifically,a plurality of sheetlike resin members stretched so as to receive thelower wall.

[0021] Another specific example of the elastically deformable supportmember is a plurality of wirelike resin members stretched so as toreceive the lower wall.

[0022] Another specific example of the elastically deformable supportmember is a foamed member on which the lower wall is mounted.

[0023] Another specific example of the elastically deformable supportmember is a spring member on which the lower wall is mounted.

[0024] Still another specific example of the elastically deformablesupport member is a rubber member on which the lower wall is mounted.

[0025] Here, for example, where the upper wall is arranged to be curvedupward according to the increase in the fuel amount in order to furtherincrease the amount of fuel to be stored in the fuel storage chamber,the fuel storage chamber is more curved downward than the upwardcurvature of the upper wall with increase of the fuel amount, because ofthe weight of the fuel storage chamber including the fuel. Therefore,deformation amounts of the upper wall and the lower wall are differentfrom each other, which could result in twisting and in turn breaking theperipheral walls connecting them and making the capacity of the fuelstorage chamber instable. Further, where a fuel meter (gage) formeasuring the fuel amount of the fuel storage chamber is constructed tomeasure the fuel amount, for example, according to the deformation ofthe upper wall or the lower wall, the measurement will be inaccurate.

[0026] In contrast with it, the elastically deformable support memberpermits the downward curvature of the lower wall while receiving theweight of the fuel storage chamber including the fuel, as describedabove, so that the deformation amounts of the upper wall and the lowerwall can be equalized. This prevents the breakage due to the twisting ofthe peripheral walls, stabilizes the capacity of the fuel storagechamber, and permits accurate measurement of the fuel amount.

[0027] When the support member is configured to have deformation amountadjusting means, which abuts against the lower wall, for adjusting adeformation amount of the downward curvature of the lower wall so as tomatch with a deformation amount of curvature of the upper wall, thedeformation amounts of the upper wall and the lower wall become nearlyequal to each other, which prevents the breakage due to the twisting ofthe peripheral walls, which stabilizes the capacity of the fuel storagechamber, and which permits the accurate measurement of the fuel amount.

[0028] In a preferred configuration there is provided curvaturedeformation regulating means for regulating the downward curvature ofthe lower wall at predetermined magnitude, below the fuel storagechamber. When this configuration is employed, the curvature deformationregulating means provided below the fuel storage chamber regulates thedownward curvature of the lower wall at the predetermined magnitude, sothat the lower wall is not deformed excessively over the predeterminedmagnitude. This protects the lower wall.

[0029] The curvature deformation regulating means is preferably anauxiliary fuel tank, located below the fuel storage chamber andconnected to the fuel storage chamber, for temporarily storing the fuelfrom the fuel storage chamber. When this configuration is adopted, theauxiliary fuel tank is utilized as the curvature deformation regulatingmeans and there is, therefore, no dead space below the fuel storagechamber. Therefore, this compactifies the fuel tank and, further,improves mountability of the whole fuel tank including the auxiliaryfuel tank. In addition, the fuel in the fuel storage chamber is suppliedto the auxiliary fuel tank with reliability, because the auxiliary fueltank is located below the fuel storage chamber.

[0030] The auxiliary fuel tank is preferably configured in a shape tomatch with the shape of the lower wall during the downward curvature ofthe lower wall. When this configuration is employed, protection of thelower wall is further enhanced, because the shape of the auxiliary fueltank matches with the shape of the lower wall during the downwardcurvature of the lower wall.

[0031] The present invention will be more fully understood from thedetailed description given hereinbelow and the accompanying drawings,which are given by way of illustration only and are not to be consideredas limiting the present invention.

[0032] Further scope of applicability of the present invention willbecome apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention will beapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a partial sectional view to show a fuel storageapparatus provided with the fuel tank of the first embodiment;

[0034]FIG. 2 is a perspective view to show the basic shape of the fueltank;

[0035]FIG. 3 is a perspective view to show a state of the fuel tank inwhich the fuel is full;

[0036]FIG. 4 is a sectional view taken along line X-X of FIG. 3;

[0037]FIG. 5 is a perspective view to show a state of the fuel tank inwhich the fuel is little;

[0038]FIG. 6 is a sectional view taken along line X-X of FIG. 5;

[0039]FIG. 7 is a sectional plan view to show the auxiliary fuel tank;

[0040]FIG. 8 is a detailed sectional view to show an enlarged view ofpart A in FIG. 1;

[0041]FIG. 9 is a detailed sectional view, similar to FIG. 8, to show afuel storage apparatus provided with the fuel tank of the secondembodiment;

[0042]FIG. 10 is a schematic plan view to show the fuel tank of thesecond embodiment;

[0043]FIG. 11 is a detailed sectional view, similar to FIG. 8, to show afuel storage apparatus provided with the fuel tank of the thirdembodiment;

[0044]FIG. 12 is an explanatory drawing to show a state of vibrationisolation of the fuel tank of FIG. 11;

[0045]FIG. 13 is a detailed sectional view, similar to FIG. 8, to show afuel storage apparatus provided with the fuel tank of the fourthembodiment;

[0046]FIG. 14 is an explanatory drawing to show a state of vibrationisolation of the fuel tank of FIG. 13;

[0047]FIG. 15 is a detailed sectional view, similar to FIG. 8, to show afuel storage apparatus provided with the fuel tank of the fifthembodiment;

[0048]FIG. 16 is an explanatory drawing to show a state of vibrationisolation of the fuel tank of FIG. 15;

[0049]FIG. 17 is a partial sectional view to show a fuel storageapparatus provided with the fuel tank of the sixth embodiment;

[0050]FIG. 18 is a plan view to show the major part of a fuel storageapparatus provided with the fuel tank of the seventh embodiment;

[0051]FIG. 19 is a sectional view taken along line Y-Y of FIG. 18;

[0052]FIG. 20 is a plan view to show the major part of a fuel storageapparatus provided with the fuel tank of the eighth embodiment;

[0053]FIG. 21 is a sectional view taken along line Z-Z of FIG. 20;

[0054]FIG. 22 is a sectional structural diagram to show the major partof a fuel storage apparatus provided with the fuel tank of the ninthembodiment;

[0055]FIG. 23 is a sectional structural diagram to show the major partof a fuel storage apparatus provided with the fuel tank of the tenthembodiment; and

[0056]FIG. 24 is a sectional structural diagram to show the major partof a fuel storage apparatus provided with the fuel tank of the eleventhembodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] The preferred embodiments of the fuel tank according to thepresent invention will be described with reference to the accompanyingdrawings. In the figures, the same elements will be denoted by the samereference symbols and redundant description will be omitted.

[0058] The fuel tank of the present invention is used as a tank forstoring the fuel to be supplied, for example, to an internal combustionengine. Of course, it can also be used as a tank for simply storing thefuel.

[0059]FIG. 1 is a partial sectional view to show a fuel storageapparatus provided with the fuel tank of the first embodiment. This fuelstorage apparatus 1 has a housing (also called a tank shell) 4constituting the outer shell of the fuel storage apparatus 1. Thishousing 4 is made of a rigid member, such as metal or synthetic resin,and is composed of an upper portion 2 and a lower portion 3 separated upand down from each other. The upper portion 2 has an upwardly curvedshape and the lower portion 3 has a downwardly curved shape. These upperand lower portions 2, 3 are hermetically connected to each other atflanges 2 a, 3 a formed around the entire periphery of each portion.

[0060] Inside an inner space defined by the upper portion 2 and lowerportion 3 of the housing 4, there is a partition wall 6 (see FIG. 2) ofa hexahedron, and this partition wall 6 partitions the inner space inthe housing 4 into a fuel storage chamber 5 inside the partition wall 6and upper and lower spaces 61 a, 61 b outside the partition wall 6. Thepartition wall 6 and fuel storage chamber 5 compose a fuel tank 70.

[0061] The partition wall 6 forming the fuel tank 70 has the basic shapeof substantially a rectangular parallelepiped, as illustrated in FIG. 2,and is comprised of a pair of substantially rectangular upper wall 7 andlower wall 8 opposed to each other in the vertical direction, and foursubstantially rectangular side walls (peripheral walls) 9 a to 9 d forconnecting (or closing) corresponding edges of these upper wall 7 andlower wall 8 to each other. These side walls 9 a to 9 d are connected sothat their both edges are connected to edges of other adjacent sidewalls and connecting portions 9 e to 9 h are formed between the sidewalls 9 a to 9 d.

[0062] The partition wall 6 having these upper wall 7, lower wall 8, andside walls 9 a to 9 d is formed, for example, in multilayered structurein which a skin layer of high-density polyethylene covers the bothsurfaces of the flat core part made of ethylene-vinyl copolymer resin ornylon. The partition wall 6 of this structure is substantially rigid anddeformable.

[0063] The area of the upper wall 7 or the lower wall 8 is larger thanthe area of one side wall and the rigidity of the upper wall 7 and thelower wall 8 is smaller than that of the side walls 9 a to 9 d.

[0064] Here, the upper wall 7 and lower wall 8 are not limited to therectangular walls, but may be a pair of polygonal walls. Accordingly,the upper wall 7 and lower wall 8 correspond to the polygonal walls, andthe side walls 9 a to 9 d to the connecting walls connecting the upperwall 7 and the lower wall 8. The shapes of the upper wall 7, lower wall8, and side walls 9 a to 9 d are properly selected, depending upon theshape of the space for the fuel tank 70 to be mounted.

[0065] As described above, the fuel storage chamber 5 of thesubstantially rectangular parallelepiped shape in the basic shape of thepartition wall 6 is defined inside the partition wall 6. After withsupply of the fuel into the fuel storage chamber 5 the fuel amount inthe fuel storage chamber 5 exceeds one at which the rectangularparallelepiped shape can be maintained (hereinafter referred to aspredetermined amount), the upper wall 7 and lower wall 8 move away fromeach other to be curved so as to inflate outward while the side walls 9a to 9 d approach each other to be curved so as to be indented inward,as illustrated in FIG. 3 and FIG. 4.

[0066] More specifically, as the fuel amount in the fuel storage chamber5 increases over the predetermined amount, the upper wall 7 suffersinflation due to the increase in the fuel amount to be curved so as towarp vertically upward, the lower wall 8 suffers inflation due to theincrease in the fuel amount and the weight of the fuel to be curved soas to warp vertically downward, and the side walls 9 a to 9 d becomecurved so as to warp horizontally and inwardly. In this way the amountof the fuel that can be stored in the fuel storage chamber 5 increasesgradually.

[0067] On the other hand, as the fuel is discharged from the fuelstorage chamber 5 so as to decrease the fuel amount in the fuel storagechamber 5 below the predetermined amount, the upper wall 7 and lowerwall 8 move toward each other to be curved so as to be indented inwardand the side walls 9 a to 9 d also move toward each other to be curvedso as to be indented inward, as illustrated in FIG. 5 and FIG. 6.

[0068] More specifically, as the fuel amount in the fuel storage chamber5 decreases below the predetermined amount, the upper wall 7 becomescurved so as to warp downward, the lower wall 8 becomes curved so as towarp upward, and the side walls 9 a to 9 d becomes curved so as to warphorizontally and inwardly. In this way the amount of the fuel that canbe stored in the fuel storage chamber 5 decreases gradually.

[0069] Deformation amounts of the upper wall 7 and the lower wall 8 aregreater than those of the side walls 9 a to 9 d. Accordingly, the upperwall 7 and lower wall 8 serve as large deformation surfaces, and theside walls 9 a to 9 d as small deformation surfaces.

[0070] Again referring to FIG. 1, a fuel pipe 60 for supplying ordischarging the fuel into or from the fuel storage chamber 5 isconnected to the approximate center of the lower wall 8 forming thepartition wall 6. This fuel pipe 60 is branched below the lower wall 8into a fuel supply pipe 10 and a fuel inlet pipe 20 connected to anauxiliary fuel tank 14 described hereinafter.

[0071] The fuel supplied through a fuel inlet (not illustrated) issupplied through the fuel supply pipe 10 and fuel pipe 60 into the fuelstorage chamber 5 and is also supplied through the fuel inlet pipe 20into the auxiliary fuel tank 14. During discharge of the fuel, the fuelin the fuel storage chamber 5 is sucked through the fuel pipe 60 andfuel inlet pipe 20 into the auxiliary fuel tank 14.

[0072] These fuel supply pipe 10 and fuel inlet pipe 20 permit thecurvature deformation of the lower wall 8, because their pipe walls areformed in the bellows shape to be extensible and bendable at theconnection to the fuel pipe 60. In the present embodiment the fuel inletpipe 20 is formed in the bellows shape throughout the entire lengththereof.

[0073] An evaporated fuel exhaust pipe 11 for discharging the gas,particularly the evaporated fuel, from the fuel storage chamber 5 to theoutside of the fuel storage chamber 5 is connected through an isolationvalve 12 to the approximate center of the upper wall 7 forming thepartition wall 6. This evaporated fuel exhaust pipe 11 is flexible andpermits the curvature deformation of the upper wall 7. The isolationvalve 12 isolates the evaporated fuel exhaust pipe 11 to prevent thefuel from leaking to the outside of the fuel storage chamber 5 when thefuel level of the fuel storage chamber 5 reaches the isolation valve 12.

[0074] The evaporated fuel exhaust pipe 11 is connected through a checkvalve 13 and a charcoal canister (not illustrated) for temporarilyadsorbing the evaporated fuel to a suction passage (not illustrated) ofthe internal combustion engine. The evaporated fuel adsorbed to thischarcoal canister is discharged into the suction passage to be burned,according to the engine operating status of the internal combustionengine.

[0075] The above check valve 13 is opened when the pressure inside theevaporated fuel exhaust pipe 11 between the check valve 13 and theisolation valve 12 becomes over a positive pressure preliminarilydetermined. It is closed when the pressure is below the predeterminedpositive pressure. This action of the check valve 13 prevents the gasfrom flowing into the fuel storage chamber 5 after the isolation valve12 has isolated the pipe 11.

[0076] Further, on the internal wall surface of the upper portion 2 ofthe housing 4 there is provided a fuel gage 71 for detecting adisplacing position or a moving amount of the upper wall 7 in thevertical direction and for calculating the fuel amount in the fuelstorage chamber 5. This fuel gage 71 is a pendulum type gage whichcomputes the fuel amount from an angle of displacement of a pendulum.

[0077] The auxiliary fuel tank 14 for temporarily storing the fuel fromthe fuel storage chamber 5 is located on the lower portion 3 of thehousing 4 and below the lower wall 8 on the side between the fuel pipe60 and the side wall 9 c. Placed inside this auxiliary fuel tank 14 is afuel pump 16 for feeding the fuel from the auxiliary fuel tank 14through a fuel feed pipe 15 to fuel injection valves (not illustrated)of the internal combustion engine. This fuel pump 16 sucks in the fuelthrough a filter 17 for filtering dust or the like in the fuel and feedsthe fuel to the fuel injection valves with controlling the pressure ofthe fuel to a predetermined value.

[0078] A separation wall 18 extending substantially vertically up standson a lower wall 50 of the auxiliary fuel tank 14. This separation wall18 is placed so as to surround the fuel pump 16 and filter 17, asillustrated in FIG. 7, to form an accommodation chamber 19 foraccommodating the fuel pump 16 and filter 17, thereby preventing thefuel around the filter 17 from being drained away when the auxiliaryfuel tank 14 is inclined so as to incline the fuel level in theauxiliary fuel tank 14. Accordingly, this separation wall 18 functionsas fuel drain preventing means.

[0079] As illustrated in FIG. 1, an upper surface of an upper wall 52 ofthe auxiliary fuel tank 14 and an upper surface of part 3 a below thelower wall 8 on the side between the fuel pipe 60 and the side wall 9 a,in the lower portion 3 of the housing 4 (the part 3 a will be referredto simply as predetermined part of the lower portion 3) match with theshape of the lower wall 8 when the lower wall 8 of the partition wall 6is curved downward; and a lower surface of the upper portion 2 of thehousing 4 matches with the shape of the upper wall 7 when the upper wall7 of the partition wall 6 is curved upward.

[0080] When the lower wall 8 is curved downward to go into contact withthe upper wall 52 of the auxiliary fuel tank 14 and with the uppersurface of the predetermined part 3 a of the lower portion 3 of thehousing 4, the upper wall 52 and the predetermined part 3 a of the lowerportion 3 prevent the lower wall 8 from being further curved downward,thereby regulating the downward curvature of the lower wall 8 atpredetermined magnitude; when the upper wall 7 is curved upward to gointo contact with the lower surface of the upper portion 2 of thehousing 4, the upper portion 2 prevents the upper wall 7 from beingfurther curved upward, thereby regulating the upward curvature of theupper wall 7 at predetermined magnitude. The magnitudes of the curvaturedeformations thus regulated are those equivalent to the full tank amountof fuel, for example.

[0081] Therefore, the upper wall 52 of the auxiliary fuel tank 14, thepredetermined part 3 a of the lower portion 3 of the housing 4, and theupper portion 2 of the housing 4 work each as curvature deformationregulating means for regulating the curvature of the lower wall 8 or theupper wall 7 at the predetermined magnitude.

[0082] Accordingly, the lower wall 8 and upper wall 7 of the partitionwall 6 are prevented from being curved excessively over thepredetermined allowable level, by the upper wall 52 of the auxiliaryfuel tank 14, the predetermined part 3 a of the lower portion 3 of thehousing 4, and the upper portion 2 of the housing 4. The upper wall 7and lower wall 8 are thus protected during the curvature deformation. Inaddition, the upper wall 7 and lower wall 8 are further protected duringthe curvature deformation, because the shape of the upper wall 52 of theauxiliary fuel tank 14 and the predetermined part 3 a of the lowerportion 3 of the housing 4 matches with the shape of the downwardcurvature of the lower wall 8 while the shape of the upper portion 2 ofthe housing 4 matches with the shape of the upward curvature of theupper wall 7. The upper wall 7 and lower wall 8 are protected in thisway, thereby preventing deterioration of or damage to the fuel tank 70due to excess deformation.

[0083] Since the upper wall 52 of the auxiliary fuel tank 14 is utilizedfor prevention of deformation of the lower wall 8 as described above,there is no dead space below the partition wall 6, the whole of the fuelstorage apparatus 1 is compactified, and the mountability of the fuelstorage apparatus 1 is improved. In addition, the fuel in the fuelstorage chamber 5 is supplied to the auxiliary fuel tank 14 withreliability, because the auxiliary fuel tank 14 is located below thefuel storage chamber 5.

[0084] The supply of the fuel through the fuel supply pipe 10 into thefuel storage chamber 5 is stopped when the lower wall 8 of the partitionwall 6 comes to contact the upper wall 52 of the auxiliary fuel tank 14and the top surface of the predetermined part 3 a of the lower portion 3of the housing 4 and when the upper wall 7 of the partition wall 6 comesto contact the lower surface of the upper portion 2 of the housing 4.Namely, the maximum storage amount of the fuel in the fuel storagechamber 5 is determined by the upper wall 52 of the auxiliary fuel tank14, the predetermined part 3 a of the lower portion 3 of the housing 4,and the upper portion 2 of the housing 4.

[0085] From this reason, the upper wall 52 of the auxiliary fuel tank14, the predetermined part 3 a of the lower portion 3 of the housing 4,and the upper portion 2 of the housing 4, working as the curvaturedeformation regulating means, also serve each as fuel storage amountdefining means for defining the maximum amount of the fuel that can bestored in the fuel storage chamber.

[0086] Inside the entire circumference of the housing peripheral partconnecting the upper portion 2 and lower portion 3 of the housing 4, asillustrated in FIG. 1 and FIG. 8, a space 21 having approximately thesame height as that of the side walls 9 a to 9 d of the partition wall 6is formed by the upper portion 2 and the lower portion 3. Accommodatedin this space 21 are the side walls 9 a to 9 d and connecting portions22 of the upper and lower walls 7, 8 connected to the side walls 9 a to9 d. Regarding the connecting portions 22 of the upper and lower walls7, 8 as parts of the side walls, the connecting portions 22 of the upperand lower walls 7, 8 and the side walls 9 a to 9 d together will becalled a side-wall-equivalent portion 62, which corresponds to theperipheral part of the partition wall 6 (fuel tank 70).

[0087] In this way the partition wall 6 is supported so as to behorizontally slidable relative to the housing 4 while theside-wall-equivalent part 62 is pinched by the upper portion 2 and thelower portion 3 of the housing 4. Namely, the housing peripheral partconnecting the upper portion 2 and lower portion 3 of the housing 4constitutes a pinching portion 23 which horizontally slidably pinchesthe side-wall-equivalent part 62 of the partition wall 6 (see FIG. 8).This pinching portion 23 functions as a support member for supportingthe partition wall 6.

[0088] The above side-wall-equivalent part 62 is displaced ashorizontally sliding in the pinching portion 23 during the curvaturedeformation of the upper wall 7 and lower wall 8. During the curvaturedeformation of the upper wall 7 and lower wall 8, upward and downwarddisplacement of the connecting portions 22 of the upper wall 7 and lowerwall 8 is very small relative to the upper wall 7 and lower wall 8.Therefore, as illustrated in FIG. 8, the pinching portion 23 does notrestrain the upward and downward curvature deformation of the upper wall7 and lower wall 8.

[0089] Since the partition wall 6 is supported at theside-wall-equivalent part 62 by the pinching portion 23 of the housing 4in this way, the upper wall 7 and lower wall 8 are permitted to undergothe upward and downward curvature deformation according to the fuelamount in the fuel storage chamber 5.

[0090] In the fuel tank 70 constructed as described above, the fuel issupplied through the fuel supply pipe 10 into the partition wall 6 thebasic shape of which is the substantially rectangular parallelepipedshape illustrated in FIG. 2, and with increase of the fuel amount in thefuel storage chamber 5 over the aforementioned predetermined amount, theupper wall 7 becomes curved upward and the lower wall 8 becomes curveddownward, while the side walls 9 a to 9 d become curved inward. Thesecurvatures gradually increase according to the increase in the fuelamount without being restrained by the pinching portion (support member)23 supporting the fuel tank 70, so as to increase the capacity of thefuel storage chamber 5, whereby the fuel can be stored up to the maximumin the fuel storage chamber 5. At this time the fuel is also chargedinto the auxiliary fuel tank 14.

[0091] As described above, the present embodiment is adapted so that thegreater amount of the fuel can be stored in the fuel storage chamber 5than in the fuel tank inhibiting the upward curvature of the upper wall7 and the downward curvature of the lower wall 8 with increase in thefuel amount. Because of this structure, the amount of the fuel that canbe stored in the fuel storage chamber 5 can be maintained at themaximum.

[0092] On the other hand, in the fuel discharge operation the fuel pumpis actuated to feed the fuel from the fuel storage chamber 5 through thefuel pipe 60, fuel inlet pipe 20, filter 17, and fuel feed pipe 15 tothe fuel injection valves of the internal combustion engine. The upwardcurvature of the upper wall 7, the downward curvature of the lower wall8, and the inward curvature of the side walls 9 a to 9 d becomegradually relaxed with decrease of the fuel amount in the fuel storagechamber 5 and then the partition wall 6 returns to the substantiallyrectangular parallelepiped shape illustrated in FIG. 2 when the fuelamount of the fuel storage chamber 5 is decreased to the predeterminedamount.

[0093] As the fuel is further fed from the fuel storage chamber 5 so asto decrease the fuel amount in the fuel storage chamber 5 to below thepredetermined amount, the negative pressure due to suction makes theupper wall 7 curved downward, the lower wall 8 curved upward, and theside walls 9 a to 9 d curved inward as illustrated in FIG. 5. Thesecurvatures gradually increase according to the decrease of the fuelamount without being restrained by the pinching portion 23 supportingthe fuel tank 70. When the upper wall 7 becomes abutting against thelower wall 8 approximately at their center to be in close contacttherewith, as illustrated in FIG. 6, further curvature deformation isstopped.

[0094] As described above, the present embodiment is adapted so that thecapacity of the space in the fuel storage chamber 5 is decreased morethan in the fuel tank inhibiting the lower curvature of the upper wall 7and the upper curvature of the lower wall 8 with decrease in the fuelamount, by the degree corresponding to the capacity of the fuel storagechamber 5 decreased by the curvatures. Because of this structure, theevaporated fuel is decreased drastically.

[0095] Incidentally, when the fuel storage apparatus 1 is mounted on avehicle, the vibration of the vehicle may vibrate the fuel tank 70 upand down (i.e., vertical G may vibrate it). Increase of the verticalvibration of this fuel tank 70 will produce noise or damage theside-wall-equivalent portion 62 of the fuel tank 70 supported by thepinching portion 23 of the housing 4. The second embodiment is thusarranged to suppress the vertical vibration of the fuel tank 70 withoutrestraining the curvature deformation of the fuel tank 70.

[0096] Referring to FIG. 9 and FIG. 10, the second embodiment is adaptedso that vibration-isolating members (elastic members) 25 of rubberhaving elasticity, for example, are interposed each between the fourcorners 24 of the partition wall 6 (fuel tank 70) and the pinchingportion 23 of the housing 4.

[0097] Here, the vibration-isolating members 25 are made of rubber andthe partition wall 6 is made of resin as described previously;therefore, the side-wall-equivalent portion 62 is hard to slide relativeto the vibration-isolating members 25.

[0098] In this second embodiment the vibration-isolating members 25 are,therefore, provided at the four corners 24 (parts of theside-wall-equivalent portion 62) which have the connecting portions 9 eto 9 h connecting the upper wall 7, the lower wall 8, and adjacent sidewalls and which have the highest rigidity, as compared with the otherportions, and thus undergo little deformation.

[0099] Therefore, the deformation of the side walls 9 a to 9 d, theupper wall 7, and the lower wall 8 will not be suppressed even if thecorners 24 are supported through the vibration-isolating members 25 bythe pinching portion 23; and then, the side walls 9 a to 9 d, the upperwall 7, and the lower wall 8 can undergo the curvature deformationsimilar to that in the first embodiment.

[0100] Since the corners 24 have the high rigidity as described above,the partition wall 6 can be supported well even in the structuresupporting only the corners 24.

[0101] Because of this structure supporting only the corners 24, thestructure becomes simpler than the first embodiment supporting the wholeof the side-wall-equivalent portion 62.

[0102] In this second embodiment constructed as described above, whenthe fuel tank 70 vibrates vertically, this vibration is transmitted tothe vibration-isolating members 25 and the elastic action of thevibration-isolating members 25 suppresses the vertical vibration.Accordingly, the vibration-isolating members 25 correspond to verticalvibration suppressing means out of vibration suppressing means forsuppressing (or attenuating) input of vibration from the outside of thefuel storage chamber 5 thereinto. This suppresses the damage to the fueltank 70 and the production of noise.

[0103] The vibration-isolating characteristics of thevibration-isolating members 25, which are frequencies of vibration thatcan be prevented by the vibration-isolating members 25, differ dependingupon the elastic modulus of the vibration-isolating members 25.Therefore, the elastic modulus of the vibration-isolating members 25 isproperly selected according to the frequencies of the vertical vibrationof the fuel tank 70 to be suppressed. The other structure, operation,and effect of the second embodiment are the same as those of the firstembodiment and are thus omitted to explain herein.

[0104] Incidentally, when the fuel tank 70 is mounted on the vehicle, itis vibrated laterally by acceleration G (in front and back directions ofthe vehicle or in horizontal directions of the vehicle), which mayproduce the noise or damage the corners 24 of the side-wall-equivalentportion 62 supported by the housing 4. The third embodiment is thusarranged to suppress the vertical vibration of the fuel tank 70 and alsosuppress the lateral vibration thereof.

[0105] In the third embodiment, as illustrated in FIG. 11, coil springs52 as elastic members are located in place of the vibration-isolatingmembers 25 of the second embodiment. The coil springs 52 extend andcontract so as to permit the vertical and lateral vibration of the fueltank 70, as illustrated in FIG. 12.

[0106] The coil springs 52 thus suppress the vertical vibration of thefuel tank 70 and also suppress the lateral vibration of the fuel tank 70by their elastic action. Accordingly, the coil springs 52 function asvibration (vertical and lateral vibration) suppressing means. The otherstructure, operation, and effect of the third embodiment are the same asthose of the second embodiment and thus the description thereof isomitted herein.

[0107] Meanwhile, in the second embodiment and third embodiment, thefuel tank 70 is supported only at the four corners 24 by the pinchingportion 23 of the housing 4. Because of this structure, the supportstrength of the fuel tank 70 to the housing 4 is small and the housing 4could fail to support the fuel tank 70 when the vibration of the fueltank 70 is great. The fourth embodiment is thus arranged to suppress thevertical and lateral vibration of the fuel tank 70 and to enhance thesupport strength of the fuel tank 70 to the housing 4.

[0108] In this fourth embodiment, as illustrated in FIG. 13, flanges(flange members) 26 extending laterally and outwardly horizontally fromthe side walls 9 a to 9 d are formed integrally with the side walls 9 ato 9 d. The flanges 26 are formed at the four corners 24 of the fueltank 70. A flange through hole 27 vertically penetrating each flange 26is formed in the central part of the flange 26 and a pair of secondvibration-isolating members (elastic members) 28 of rubber havingelasticity, for example, are located between the flange 26 and the upperportion 2 or the lower portion 3 (the pinching portion 23), i.e., on theboth sides of the flange 26 in the vertical direction. Through thecentral portions of these second vibration-isolating members 28, 28,isolator through holes 29 vertically penetrating the secondvibration-isolating members 28 are formed each coaxially with the flangethrough hole 27.

[0109] In a wall surface of each second vibration-isolating member 28 incontact with the flange 26, a groove or recess 30 is formed so as tosurround the isolator through hole 29. Namely, each of the secondvibration-isolating members 28 is provided with two legs 31 in contactwith the flange 26. Further, an upper portion through hole 32 and alower portion through hole 33 perpendicularly penetrating the upperportion 2 and lower portion 3 are formed coaxially with the isolatorthrough hole 29, in the upper portion 2 and lower portion 3 (pinchingportion 23). A collar 34 is inserted through these upper portion throughhole 32, isolator through hole 29, flange through hole 27, and lowerportion through hole 33. A bolt 35 is inserted into this collar 34 andthis bolt 35 is fastened by a nut 36. The inside diameter of the flangethrough hole 27 is larger than the outside diameter of the collar 34.

[0110] In the fourth embodiment constructed as described above, theflange 26 is firmly fastened so as to be slidable relative to the upperportion 2 and lower portion 3 (pinching portion 23), through the secondvibration-isolating members 28 by the collar 34, bolt 35, and nut 36.Therefore, the support strength of the fuel tank 70 to the housing 4 ishigher than those in the second and third embodiments.

[0111] Since the inside diameter of the flange through hole 27 is largerthan the outside diameter of the collar 34, the side walls 9 a to 9 dcan be displaced laterally. Accordingly, the flanges 26 serve as slidesupport portions (the peripheral part of the partition wall 6) slidablysupported relative to the housing 4.

[0112] With the lateral displacement of the side walls 9 a to 9 d, thetwo legs 31 of each second vibration-isolating member 28 are laterallydisplaced following the flange 26 because of their elastic action, asillustrated in FIG. 14. Thanks to this structure, the secondvibration-isolating members 28 do not inhibit the lateral displacementof the side walls 9 a to 9 d and the second vibration-isolating members28 suppress the lateral vibration of the fuel tank 70. Accordingly, thesecond vibration-isolating members 28 correspond to lateral vibrationsuppressing means. Of course, the second vibration-isolating members 28also suppress the vertical vibration. Therefore, the secondvibration-isolating members 28 also correspond to vertical vibrationsuppressing means. The other structure, operation, and effect of thefourth embodiment are the same as those of the second embodiment and thedescription thereof is omitted herein.

[0113] Incidentally, the fourth embodiment is arranged to suppress thelateral vibration of the fuel tank 70, but the legs 31 of the secondvibration-isolating members 28 are displaced largely according to thehorizontal vibration of the fuel tank 70. Therefore, the secondvibration-isolating members 28 except for the legs 31 do not contributeto the suppression of the lateral vibration. This means that the lateralvibration suppressing effect of the fuel tank 70 is rather weak in thefourth embodiment. The fifth embodiment is thus arranged to enhance thelateral vibration suppressing effect of the fuel tank 70.

[0114] In the fifth embodiment, as illustrated in FIG. 15, thirdvibration-isolating members 37, for example, of rubber having elasticityare placed on the both sides of the flanges 26 in the verticaldirection. These third vibration-isolating members 37 are each incontact with the flange 26 through a collar 38, for example, of metaland are fixed each to the upper portion 2 or to the lower portion 3(pinching portion 23) through a collar 39, for example, of metal. A bolt40 is buried in the upper part of the lower third vibration-isolatingmember 37 while a nut 41 is buried in the lower part of the upper thirdvibration-isolating member 37. Then the bolt 40 is inserted through theabove flange through hole 27 to be fastened by the nut 41.

[0115] In the fifth embodiment, as illustrated in FIG. 16, when the sidewalls 9 a to 9 d of the fuel tank 70 are displaced laterally, the thirdvibration-isolating members 37 follow this displacement to be deformedbecause of their elastic action. At this time, the thirdvibration-isolating members 37 are totally deformed, so as to suppressthe lateral vibration of the fuel tank 70. Accordingly, the thirdvibration-isolating members 37 function as lateral vibration suppressingmeans. Since the third vibration-isolating members 37 are totallydeformed as described above, the lateral vibration of the fuel tank 70is more suppressed than in the fourth embodiment. The other structure,operation, and effect of the fifth embodiment are the same as those ofthe second embodiment and the description thereof is omitted herein.

[0116] Incidentally, there are cases where the fuel pump 16 has to beinstalled vertically because of the shape of the space for placement ofthe fuel storage apparatus 1 and piping. The sixth embodiment is thusadapted for the vertical placement of the fuel pump 16.

[0117] As illustrated in FIG. 17, the auxiliary fuel tank 14 forming thefuel storage apparatus 1 is placed in a side portion of the housing 4,and the filter 17 and the fuel pump 16 vertically installed are providedin this auxiliary fuel tank 14. The auxiliary fuel tank 14 is providedwith a housing side wall portion 43 extending vertically and connectingthe upper portion 2 to the lower portion 3 of the housing 4 at the sideportion, a housing shutting wall portion 72 standing inside the housingside wall portion 43 and shutting the auxiliary fuel tank from the fueltank 70, and a space portion 73 defined by these housing side wallportion 43, housing shutting wall portion 72, upper portion 2, and lowerportion 3 and including the above fuel pump 16 and filter 17. Thehousing shutting wall portion 72 has a deformation regulating wall 49 ascurvature deformation regulating means in the lower side thereof nearthe fuel tank 70, and this deformation regulating wall 49 regulates thedownward curvature of the lower wall 8 forming the partition wall 6 atthe predetermined magnitude. The evaporated fuel in the auxiliary fueltank 14 is fed through an evaporated fuel feed pipe 51 to the charcoalcanister.

[0118] The other structure, operation, and effect of the sixthembodiment are the same as those of the first embodiment and thedescription thereof is omitted herein.

[0119] Incidentally, in the first to the sixth embodiments, the fueltank 70 experiences more downward bending of the lower wall 8 thanbending of the upper wall 7 because of the weight of the fuel tank 70including the fuel. Because of this, the magnitude of the upwardcurvature of the upper wall 7 is not coincident with the magnitude ofthe downward curvature of the lower wall 8 during the curvaturedeformation of the partition wall 6 according to the increase of thefuel amount in the fuel storage chamber 5. Namely, the curvaturedeformation amounts of the upper wall 7 and the lower wall 8 aredifferent from each other (the shapes of the upper wall 7 and lower wall8 become asymmetric), which could twist and break the side walls 9 a to9 d connecting them. In addition, the capacity of the fuel storagechamber 5 is instable. Further, the fuel measurement becomes inaccuratein the case of the pendulum type fuel gage 71 (see FIG. 1) for measuringthe fuel amount from the displacement position of the upper wall 7 asdescribed previously. The seventh embodiment is thus arranged to preventoccurrence of twisting of the side walls 9 a to 9 d during the curvaturedeformation of the partition wall 6, to stabilize the capacity of thefuel storage chamber 5, and to make the fuel measurement accurate.

[0120] In this seventh embodiment, as illustrated in FIG. 18 and FIG.19, the fuel tank 70 is supported as being accommodated in a fuel tankaccommodating section 74. This fuel tank accommodating section 74 isgenerally composed of a pair of holding portions 75 the vertical crosssection of which is the U-shape and which are placed so that recesses(gaps) 80 forming the U-shape are opposed to each other, and a pluralityof resin members 76 connecting these holding portions 75.

[0121] The resin members 76 are made, for example, of such resin aspolyacetal and in a thin plate shape (sheet shape), and a plurality ofsuch resin members 76 are provided for each of the upper side and lowerside of the holding portions 75, thereby connecting the holding portions75 to each other on the upper side and on the lower side. Then the fueltank 70 is placed in a space portion defined by the two holding portions75 and the upper and lower resin members 76.

[0122] The height of the recess portions 80 of the holding members 75 isapproximately equal to that of the side walls 9 a to 9 d of thepartition wall 6 and the side-wall-equivalent portion 62 of thepartition wall 6 (fuel tank 70) described previously is accommodated inthese recess portions 80. This side-wall-equivalent portion 62 issupported so as to be horizontally slidable relative to the holdingportions 75 while being pinched by the holding portions 75. Accordingly,the holding portions 75 work as support members (pinching portions) forhorizontally slidably pinching the side-wall-equivalent portion(peripheral part) 62 of the fuel tank 70.

[0123] Fixing portions 77 of a flat plate shape are connectedrespectively to the both ends of each holding member 75 on the lowerside. The four fixing portions 77 of the two holding portions 75 arefixed each to the peripheral part of the housing 4. With these changes,the shape of the peripheral part of the upper portion 2 and the lowerportion 3 of the housing 4 is also modified so as to be able toaccommodate the fuel tank accommodating portion 74.

[0124] In the seventh embodiment constructed as described above, thelower resin members 76 receive the weight of the fuel tank 70 includingthe fuel and are elastically deformed while dispersing the load exertedby the lower wall 8 according to the downward curvature of the lowerwall 8, so as to support the lower wall 8 with permitting the curvatureof the lower wall 8. During this curvature deformation, the upper andlower resin members 76 are extended well in the curvature deformationdirection while horizontally expanding clearances between other adjacentresin members 76 with following the curvature deformation of the upperwall 7 and lower wall 8. Accordingly, the lower resin members 76function as elastically deformable support members (support members) forsupporting the lower wall 8 while receiving the weight of the fuel tank70 including the fuel and permitting the downward curvature deformationof the lower wall 8 with eliminating the influence of the weight.

[0125] Since the lower resin members 76 permit the downward curvature ofthe lower wall with receiving the weight of the fuel tank 70 includingthe fuel, the downward curvature deformation amount of the lower wall 8becomes approximately coincident with the upward curvature deformationamount of the upper wall 7. Accordingly, the lower resin members 76 alsoserve as deformation amount adjusting means for adjusting the downwardcurvature deformation amount of the lower wall 8 so as to match with theupward curvature deformation amount of the upper wall 7 (or for makingthe downward curvature deformation amount of the lower wall 8approximately coincident with the upward curvature deformation amount ofthe upper wall 7).

[0126] The reason why the resin members 76 are also provided on theupper side is that the upward curvature deformation amount of the upperwall 7 is further equalized to the downward curvature deformation amountof the lower wall 8 by controlling the magnitude of the upward curvaturedeformation of the upper wall 7. Accordingly, the upper resin members 76also serve as the above deformation amount adjusting means.

[0127] Since the resin members 76 keep the magnitudes of the curvaturedeformations of the upper wall 7 and the lower wall 8 approximatelycoincident with each other with increase of the fuel amount, theoccurrence of twisting of the side walls 9 a to 9 d is prevented, thecapacity of the fuel storage chamber 5 is stabilized, and the fuelmeasurement is made accurate. Since the resin members 76 support thefuel tank 70 with being elastically deformed, the vibration of the fueltank 70 is suppressed, the damage to the fuel tank 70 is also prevented,and the production of noise is also restrained. Accordingly, the resinmembers 76 also work as the vibration suppressing means described above.

[0128]FIG. 20 is a plan view to show the major part of the fuel storageapparatus provided with the fuel tank of the eighth embodiment and FIG.21 is a sectional view thereof taken along line Z-Z of FIG. 20.

[0129] The eighth embodiment is different from the seventh embodiment inthat resin members 78, 79 forming meshes are used as elasticallydeformable support members, in place of the plurality of resin members76 of the thin plate shape connecting the holding portions 75 to eachother. Of course, the resin members 78, 79 as elastically deformablesupport members also serve as the aforementioned deformation amountadjusting means and as the vibration suppressing means. Each of theresin members 78, 79 forming the meshes is a wirelike resin member andthey are placed so as to cross each other up and down like seams. Inanother configuration the holding portions 75 may be connected to eachother only by the wirelike resin members 78.

[0130] It is needless to mention that this structure can also achievethe same operation and effect as the seventh embodiment.

[0131] Although the seventh and eighth embodiments are arranged so thatthe resin members 76, 78, 79 are provided corresponding to the bothupper wall 7 and lower wall 8 of the fuel tank 70 in order to equalizethe deformation amounts of the upper wall 7 and lower wall 8 with eachother, the resin members may be provided corresponding only to the lowerwall 8 so as to make the deformation amounts of the upper wall 7 andlower wall 8 approximately coincident with each other. Namely, the upperresin members can be eliminated. The number of upper resin members (thenumber of lines) can also be made smaller than the number of lower resinmembers in order to further equalize the curvature deformations of theupper wall 7 and the lower wall 8 with each other.

[0132] The elastically deformable support members 76, 78, 79 are notlimited to the resin members. Like the ninth embodiment to the eleventhembodiment illustrated in FIG. 22 to FIG. 24, the apparatus can also bearranged so that the fuel tank accommodating section 74 described in theseventh and eighth embodiments is made as a recessed case 90, the fueltank 70 is accommodated in this case 90, and the fuel tank 70 ismounted, for example, on a foamed member 91 (sponge or the like)illustrated in FIG. 22, or on spring members 92 (spring coils, platesprings, coned disk springs, etc.) illustrated in FIG. 23, or on arubber member 93 illustrated in FIG. 24, as an elastically deformablesupport member placed in the case 90. The point is that the elasticallydeformable support member can be any member that abuts against the lowerwall 8 and that supports the lower wall 8 so as to permit the curvatureof the lower wall 8 with being elastically deformed while dispersing theload exerted by the lower wall 8 according to the downward curvature ofthe lower wall 8.

[0133] The present invention was described above in detail, based on theembodiments thereof, but the present invention is not limited only tothe above embodiments. For example, the second to fifth embodimentsdescribed above were arranged so that the elastic members 25, 28, 37, 52were interposed at the corners 24 of the fuel tank 70, but the elasticmembers may be arranged to be interposed throughout the whole of theside-wall-equivalent portion 62.

[0134] In the above embodiments the fuel tank was the fuel tank 70composed of the upper wall 7 and lower wall 8 of the polygon shapeopposed to each other, and the side walls 9 a to 9 d connecting theseupper wall 7 and lower wall 8, but, without having to be limited to thefuel tank of this structure, the present invention can be applied to anyfuel tank that is provided with the fuel storage chamber deformableaccording to the amount of the fuel stored therein.

[0135] As described above, the fuel tank according to the presentinvention is so constructed that the lower wall forming the fuel storagechamber is curved downward according to the increase of the fuel amountand that at this time the support member supporting the fuel storagechamber does not restrain the downward curvature of the lower wall,whereby the capacity of the fuel storage chamber can be increased, ascompared with those inhibiting the deformation of the lower wall. As aresult, the amount of the fuel that can be stored in the fuel storagechamber can be maintained at the maximum.

[0136] From the invention thus described, it will be obvious that theinvention may be varied in many ways. Such variations are not to beregarded as a departure from the spirit and scope of the invention, andall such modifications as would be obvious to one skilled in the art areintended for inclusion within the scope of the following claims.

What is claimed is:
 1. A fuel tank comprising a fuel storage chamberwhich is deformable according to the amount of fuel stored therein,wherein said fuel storage chamber comprises a lower wall which becomescurved downward according to increase of said amount of fuel; whereinsaid fuel storage chamber is supported by a support member which permitsdownward curvature of said lower wall; and wherein said support membercomprises vibration suppressing means for suppressing input of vibrationfrom the outside of said fuel storage chamber thereinto.
 2. The fueltank according to claim 1, wherein said vibration suppressing means isan elastic member, said elastic member supporting said fuel storagechamber in a vibration-isolating manner.
 3. The fuel tank according toclaim 2, wherein said elastic member is a vibration-isolating member ofrubber.
 4. The fuel tank according to claim 2, wherein said elasticmember is a coil spring.
 5. The fuel tank according to claim 1, whereinsaid support member is an elastically deformable support member whichabuts against said lower wall and which supports said lower wall withbeing elastically deformed while dispersing a load exerted by said lowerwall according to the downward curvature of said lower wall.
 6. The fueltank according to claim 5, wherein said elastically deformable supportmember is a plurality of sheet like resin members stretched so as toreceive said lower wall.
 7. The fuel tank according to claim 5, whereinsaid elastically deformable support member is a plurality of wire likeresin members stretched so as to receive said lower wall.
 8. The fueltank according to claim 5, wherein said elastically deformable supportmember is a foamed member on which said lower wall is mounted.
 9. Thefuel tank according to claim 5, wherein said elastically deformablesupport member is a spring member on which said lower wall is mounted.10. The fuel tank according to claim 5, wherein said elasticallydeformable support member is a rubber member on which said lower wall ismounted.